US6694990B2 - Dishwasher variable dry cycle apparatus - Google Patents

Abstract

An apparatus and method for operating a dishwasher in a variable dry cycle mode is provided. The dishwasher includes a wash chamber, a heater element located within the wash chamber, a rinse aid product dispenser, and a fan unit for circulating air. The method comprises determining a temperature of the wash chamber, determining an amount of rinse aid product in the dispenser, and, based upon the determined temperature and the amount of rinse aid product, determining an optimized heater element cycle and an optimized fan unit cycle.

Description

BACKGROUND OF INVENTION

This invention relates generally to dishwashers, and more particularly, to drying cycles for dishwashers.

Typically, known dishwashers include a cabinet housing a wash chamber wherein dishes, flatware, cups and glasses, etc. are loaded onto roller-equipped racks. Washing fluid is circulated throughout the wash chamber according to a pre-designated wash cycle executable by a control mechanism. Often, the wash cycle concludes with a dry cycle that operates a heating element located within the wash chamber, as well a forced air convection system that circulates ambient air through dishwasher vents to remove humidity from the wash chamber and dry the items located therein. Conventionally, the dry cycle consists of operating the heater element and the circulation fan for a fixed time period and opening the vent for a predetermined time period. See, for example, U.S. Pat. No. 3,908,681.

While in most cases, fixed duration heating cycles may adequately dry items in the dishwasher, certain operating conditions can render the dry cycle inadequate and/or undesirable. For example, water temperature variations in dishwasher rinse cycles, which may occur for various reasons, may lead to incompletely dried items at the end of the cycle or completely dried items well in advance of when the cycle ends. Also, rinse aid products are now available that may affect the amount of time required to dry items in the dishwasher. See, for example, U.S. Pat. No. 6,210,600 B1. Hence, the presence or absence of the rinse aid may result in dry cycles that are excessive or inefficient, respectively.

In light of stringent new energy efficiency requirements and expectations, inefficient dry cycles are undesirable for both manufacturers and consumers alike.

SUMMARY OF INVENTION

In one aspect, a method for controlling a dry cycle for a dishwasher including a wash chamber and a heater element in the wash chamber is provided. The method comprises sensing a temperature of the wash chamber, and energizing the heater element for a time dependent upon the sensed temperature.

In another aspect, a method for operating a dishwasher in a variable dry cycle mode is provided. The dishwasher includes a wash chamber, a heater element located within the wash chamber, a rinse aid product dispenser, and a fan unit for circulating air. The method comprises determining a temperature of the wash chamber, determining an amount of rinse aid product in the dispenser, and, based upon the determined temperature and the amount of rinse aid product, determining an optimized heater element cycle and an optimized fan unit cycle.

In yet another aspect, a method for operating a dishwasher in a variable dry cycle is provided. The dishwasher includes a wash chamber, a heater element in the wash chamber, a rinse aid product dispenser, a fan, and a controller. The method comprises determining operating conditions of the wash chamber and the rinse aid dispenser, and operating the heater element and the fan to execute an energy efficient dry cycle dependent upon the determined conditions of the wash chamber and the rinse aid product dispenser.

In a further aspect, a dishwasher is provided which comprises a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, and a controller operatively coupled to said heater element and to said thermistor, said controller configured to operate the heater element for a selected time period determined by a thermistor reading.

In still a further aspect, a dishwasher is provided which comprises: a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, a fan unit, and a controller operatively coupled to said heater element, to said thermistor, and to said fan unit. The controller is configured to execute a variable dry cycle wherein the heater element is energized for a selected time period determined by a thermistor reading and the fan is energized for a selected time period determined by the thermistor reading.

In yet an additional aspect, a dishwasher is provided which comprises a wash chamber, a thermistor for determining a temperature of said wash chamber, a heater element located within said wash chamber, a fan unit, a rinse aid product dispenser, a transducer operatively coupled to said rinse aid product for determining an amount of rinse aid product in the dispenser, and a controller operatively coupled to said heater element, to said thermistor, to said fan unit, and to said transducer. The controller is configured operate an energy efficient dry cycle wherein said fan unit and said heater element are energized for a time determined in response to signals from said thermistor and said transducer.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevational view of an exemplary dishwasher system partially broken away.

FIG. 2 is a schematic block diagram of the dishwasher system shown in FIG.1.

FIG. 3 is a flow chart of a variable dry cycle method executable by the system shown in FIG.2.

DETAILED DESCRIPTION

FIG. 1 is a side elevational view of an exemplarydomestic dishwasher system100 partially broken away, and in which the present invention may be practiced. It is contemplated, however, that the cycle described herein may be practiced in other types of dishwashers and dishwasher systems beyonddishwasher system100 described and illustrated herein. Accordingly, the following description ofdishwasher100 is for illustrative purposes only, and the invention is in no way limited to use in a particular type of dishwasher system, forexample dishwasher system100.

Dishwasher100 includes acabinet102 having atub104 therein and forming awash chamber106.Tub104 includes a front opening (not shown in FIG. 1) and adoor assembly120 hinged at itsbottom122 for movement between a normally closed vertical position (shown in FIG. 1) whereinwash chamber106 is sealed shut for washing operation, and a horizontal open position (not shown) for loading and unloading of dishwasher contents. Upper andlower guide rails124,126 are mounted ontub side walls128 and accommodate upper and lower roller-equippedracks130,132, respectively. Each of upper andlower racks130,132 is fabricated from known materials into lattice structures including a plurality ofelongate members134, and eachrack130,132 is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outsidewash chamber106, and a retracted position (shown in FIG. 1) in which the rack is located insidewash chamber106. Conventionally, a silverware basket (not shown) is removably attached tolower rack132 for placement of silverware, utensils, and the like that are too small to be accommodated by upper andlower racks130,132.

A control panel (not shown in FIG. 1) is integrated into anescutcheon136 that is mounted todoor assembly120, or in further and/or alternative embodiments control selectors, (e.g., buttons, switches or knobs) or control displays, etc. may be mounted at a convenient location on anouter face138 ofdoor assembly120. The control panel and associated selectors and displays are coupled to known control circuitry (not shown) and control mechanisms (not shown in FIG. 1) for operating a fluid circulation assembly (not shown in FIG. 1) that circulates water and dishwasher fluid indishwasher tub104. The fluid circulation assembly is located in amachinery compartment140 located below abottom sump portion142 oftub104.

A lower spray-arm-assembly144 is rotatably mounted within alower region146 ofwash chamber106 and abovetub sump portion142 so as to rotate in relatively close proximity tolower rack132. A mid-level spray-arm assembly148 is located in an upper region ofwash chamber106 and is located in close proximity toupper rack130 and at a sufficient height abovelower rack132 to accommodate a largest item, such as a dish or platter (not shown), that is expected to be placed inlower rack132 and washed indishwasher system100. In a further embodiment, an upper spray arm assembly (not shown) is located aboveupper rack130 at a sufficient height to accommodate a tallest item expected to be placed inupper rack130, such as a glass (not shown) of a selected height.

Lower and mid-level spray-arm assemblies144,148 and the upper spray arm assembly are fed by the fluid circulation assembly, and each spray-arm assembly includes an arrangement of discharge ports or orifices for directing washing liquid onto dishes located in upper andlower racks130,132, respectively. The arrangement of the discharge ports in at least lower spray-arm assembly144 provides a rotational force by virtue of washing fluid flowing through the discharge ports. The resultant rotation of lower spray-arm assembly144 provides coverage of dishes and other dishwasher contents with a washing spray. In various alternative embodiments,mid-level spray arm148 and/or the upper spray arm are also rotatably mounted and configured to generate a swirling spray pattern above and belowupper rack130 when the fluid circulation assembly is activated anddoor assembly120 is properly closed toseal wash chamber106 for operation.

During operation, and at the conclusion of a wash cycle, a dry cycle mode of operation is typically commenced that energizes a resistive heating element (not shown in FIG. 1) to warm the air insidewash chamber106 and a known fan unit (not shown in FIG. 1) for assisted convective airflow inwash chamber106 to remove humidity fromwash chamber106 and dry washed items located therein. In one embodiment, the fan unit is attached todoor assembly120 and mixes moist air fromwash chamber106 with dry ambient air and forces the mixed air through a vent tube (not shown) indoor assembly120 according to known techniques. Air is discharged from the vent tube at a lower end ofdoor assembly120 and condensation from the air is collected and returned todishwasher sump portion142. The circulating air has been found to be a considerable aid to drying items inwash chamber106 in a timely fashion.

In further and/or alternative embodiments, fan units may be employed in addition to, or in lieu of, the above-described fan unit attached todishwasher door assembly120. A variety of forced air circulation fans in different locations in dishwashers are found in the art, and references to fan and fan unit shall refer collectively to any fan element employed to assist in drying items inwash chamber106. In other words, the inventive concepts described herein shall apply equally to various types of fan elements operable in a dry cycle mode of operation, rather than referring exclusively to a single fan element in a single location, such as the door mounted fan arrangement described above.

FIG. 2 is a block diagram of adishwasher control system150 for use with dishwasher100 (shown in FIG.1).Control system150 includes acontroller152 which may, for example, be amicrocomputer154 coupled to a dishwasheruser interface input156. An operator may enter instructions or select desired dishwasher cycles and features viauser interface input156, and adisplay158 coupled tomicrocomputer154 displays appropriate messages, indicators, a timer, and other known items of interest to dishwasher users. Amemory160 is also coupled tomicrocomputer154 and stores instructions, calibration constants, and other information as required to satisfactorily complete a selected dishwasher cycle.Memory160 may, for example, be a random access memory (RAM). In alternative embodiments, other forms of memory could be used in conjunction with RAM memory, including but not limited to electronically erasable programmable read only memory (EEPROM).

Power tosystem150 is supplied tocontroller152 by apower supply174 configured to be coupled to a power line L. Analog to digital and digital to analog convertors (not shown) are coupled tocontroller152 to implement controller inputs and executable instructions to generate controller output to afluid circulation assembly162 according to known methods.Fluid circulation assembly162 includes a water pump, water heater, water filters, etc. to deliver washing fluids and rinses to spray-arm assemblies144,148 (shown in FIG.1). In response to manipulation ofuser interface input156,controller152 monitors various operational factors of the dishwasher, and executes operator selected functions and features according to known methods. Of course,controller152 may be used to control other dishwasher elements and functions beyond that specifically described herein.

Controller152 operates the various components of fluid circulation assembly in a designated wash cycle familiar to those in the art, including dispensation of a known rinse aid product from a rinseaid product dispenser164 in the final stages of the wash cycle. The rinse aid product is a known, commercially available composition, used separately from a detergent composition, to prevent spots and film formation on wash articles.

Atransducer166 is coupled to rinseaid dispenser164 for signalingcontroller152 of operating conditions of rinseaid product dispenser164, which is influential on the efficacy of a dishwasher dry cycle. As used herein,transducer166 is broadly defined as any device or component capable of detecting a presence or amount of rinse aid product indispenser164. For example, in an illustrative embodiment,transducer166 is a known level switch that is tripped when the rinse aid product falls below a specified level. In alternative embodiments,transducer166 may comprise a known gauge mechanism, an optical system, or other type of sensor mechanism to determine the presence and/or amount of rinse aid product indispenser164.

Athermistor168 is also inputted tocontroller152 and is used to monitor a temperature of wash chamber106 (shown in FIG.1). As used, herein,thermistor168 is broadly defined as any temperature sensing element for determining an operating temperature ofdishwasher100 prior to commencement of a dishwasher dry cycle, which also is influential on the efficacy of the dry cycle. In anillustrative embodiment thermistor168 is a known resistive element with a temperature variant resistance value. In other words, the resistance of the element fluctuates with the temperature of the element according to a known relationship, and by monitoring the voltage acrossthermistor168, the temperature ofthermistor168 may be determined.

In an illustrative embodiment,thermistor168 is located in dishwasher door assembly120 (shown in FIG. 1) and in fluid communication withwash chamber106 to monitor temperature conditions. In another embodiment,thermistor168 is located in wash chamber106 (shown in FIG. 1) itself to monitor operating temperature conditions of dishwasher100 (shown in FIG. 1) in use. Conventionally thermistors are used for a variety of purposes in dishwasher operation, including but not limited to sensing of water temperature conditions to ensure, for example sanitation requirements of the wash cycle, and in a third embodiment, one of these existing thermistors may providethermistor168. For example, the thermistor in different embodiments is thermally coupled with water exiting the water pump to sense the temperature of the water in dishwasher tub104 (shown in FIG. 1) and is located, for example, in a bottom oftub104 and in fluid communication with the water stream discharged from a water pump insidedishwasher100, or mounted to a pipe (not shown) to sense the water temperature before it exits the water pump.

It is contemplated that other temperature sensing components may be used in lieu of temperature sensitive resistive elements inthermistor168 without departing from the scope of the present invention.

Once appropriately calibrated, signals supplied from rinseaid transducer166 andthermistor168 are used bycontroller152 to determine an optimized dishwasher dry cycle whereincontroller152 operates aresistive heating element170 and avent fan unit172 for mixing and circulating air to remove humidity fromwash chamber106 in a manner consistent with sensed operating conditions oftransducer166 andthermistor168. Thus, items inwash chamber106 may be appropriately dried in an energy inefficient manner. As will be seen, and unlike conventional dishwasher using fixed time dry cycles,controller152 operates a dry cycle of a varying length depending on input conditions of the dishwasher throughthermistor168 andtransducer166.

For example, in an illustrative embodiment, a dry cycle mode is determined by a final rinse water temperature, and whether or not rinse aid product is present in rinseaid dispenser164 when the dry cycle mode is entered. On-time duration values forheater element170 andfan172 are stored incontroller memory160 and indexed bymicrocomputer154 according to input condition signals supplied bythermistor168 andtransducer166. For example, a portion of an exemplary control scheme is set forth in the following look up table:

	TABLE 1
	Final Rinse	Rinse Aid	Heater	Fan
	Temperature	Present	On-time	On-time
	155° F.	No	12 minutes	24 minutes
	155° F.	Yes	8 minutes	18minutes
	170° F.	Yes	0 minutes	15 minutes

Thus, for example, if the temperature ofwash chamber106 is determined bycontroller152 to be 155° F. as sensed bythermistor168, andtransducer166 indicates that rinse aid product is present indispenser164,microcomputer154 selects a heater time duration value of 8 minutes and a fan time duration value of 18 minutes fromcontroller memory160, andheater element170 andfan172 are energized accordingly. As the sensed temperature increases prior to energizingheater element170 andfan172, the heater-on time duration value and fan on-time duration value decrease, thereby conserving energy by applying only as much energy as dictated by operating conditions to adequately dry dishes and items therein. Also, time duration values are less when rinse aid product is present than when it is not. Excessive energy consumption of fixed time dry cycles conventionally employed in known dishwashers are therefore substantially eliminated.

Using the methodology set forth above,memory160 may be located with maps or tables of various operating conditions and specific time duration values corresponding to sensed conditions for selection and execution bycontroller152.Microcomputer154, in a further embodiment, may interpolate between values in the look up table to determine appropriate time duration values forheater element170 and172. In yet another embodiment,microcomputer154 directly calculates, according to derived or empirically determined mathematical relationships, optimal energy efficient heater element and fan on-time duration values for energy efficient operation in a dry cycle mode. In still another embodiment,controller memory160 is loaded with offset constants to add or subtract to a pre-selected time duration value forheater element170 andfan172, thereby adjusting operation ofheater element170 andfan172 as conditions dictate.

In a slightly more sophisticated approach,memory160 is loaded with alternative values such as those set forth below:

	TABLE 2
	Final Rinse	Rinse Aid	Heater Element	Fan
	Temperature	Volume	Pulses	On-time

	0° C. to 45° C.	>2 cc	17	30
	0° C. to 45° C.	<2 cc	20	30
	45° C. to 55° C.	>2 cc	12	30
	45° C. to 55° C.	<2 cc	19	20
	55° C. to 65° C.	>2 cc	6	20
	55° C. to 65° C.	<2 cc	13	10
	65° C. to 70° C.	>2 cc	3	10
	65° C. to 70° C.	<2 cc	10	10
	>70° C.	>2 cc	0	10
	>70° C.	<2 cc	7	10

Thus, under the above control scheme heater element on time (in terms of controller pulses rather than elapsed time) is less when rinse aid volume is above 2 cubic centimeters, and is more when rinse aid volume is less than 2 cubic centimeters at a given temperature. Also, heater element pulses decrease as the sensed temperature increases. Fan on-time is generally independent of rinse aid volume, but decreases as the sensed temperature increases.

Therefore,heater element170 is operated for a reduced time, thereby producing less heat, as the temperature ofwash chamber106 increases, and is operated for an increased time, thereby generating more heat intowash chamber106 as the temperature falls. Additionally,heater element170 is operated for a reduced time at a given temperature when there is more than 2 cubic centimeters of rinse aid product indispenser164, thereby indicating sufficient levels of rinse aid product in the final rinse cycle that accordingly reduces a drying time of items inwash chamber106, andheater element170 is operated for an increased time at the same temperature when less than 2 cubic centimeters of rinse aid product is present indispenser164, thereby indicating insufficient amounts of rinse aid product in the final rinse cycle that accordingly increases a drying time for items inwash chamber106. As such, heat is apportioned more commensurate with needs than in conventional systems, and unnecessary heating is generally avoided. Likewise, air circulation is apportioned more commensurate with needs than in conventional systems, and unnecessary air circulation is generally avoided. Thus,controller152 executes a smart dry cycle taking into account the necessary considerations that govern energy efficiency. As compared to fixed time duration dry cycles executed in known dishwashing systems,control system150 provides an economical, energy efficient alternative.

It should now be apparent that many variations of look up tables beyond those described may be employed in alternative embodiments while achieving at least some of the advantages of the instant invention and without departing from the scope of the present invention.

FIG. 3 is a flow chart of amethod200 executable by controller152 (shown in FIG. 2) to accomplish the foregoing advantages of an energy efficient variable length dishwasher dry cycle.

Once the activated by a user, such as with user interface input156 (shown in FIG.2),controller152 begins by inputting204 a temperature of dishwasher100 (shown in FIG.1). In illustrative embodiments, this may be accomplished by reading206 a sensed temperature signal indicative of a temperature ofwash chamber106, or by reading208 a signal indicative of a water temperature in a final rinse cycle. These signals may be generated by thermistor168 (shown in FIG. 2) for processing by microcomputer154 (shown in FIG.2).

After inputting204 a temperature signal,controller152 also inputs210 a condition of rinse aid product dispenser164 (shown in FIG.2). In illustrative embodiments, this may be accomplished by reading212 a signal fromtransducer166 ormicrocomputer154 may calculate or regulate214 an amount of rinse aid product being used in operation of the dishwasher.

Once dishwasher temperature and rinse aid volume are sensed, calculated or otherwise determined,controller152 determines216 a heater on-time duration value and also determines218 a fan on-time duration value. In accordance with exemplary embodiments, respective time duration values are calculated220,222 bycontroller152 or selected224,226 from a look up table, such as those described above. Once the heater element on-time duration value and fan on-time duration value are determined,controller152 energizes and operates228,230 the respective heater element and fan unit accordingly for a time corresponding to the determined duration values.

While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.

Claims (6)

What is claimed is:

1. A dishwasher comprising:

a wash chamber;

a thermistor for determining a temperature of said wash chamber;

a heater element located within said wash chamber for heating air in said wash chamber, and

a controller operatively coupled to said heater element and to said thermistor, said controller configured to operate the heater element for a selected dry cycle time period determined by a thermistor reading of a final rinse water temperature.

2. A dishwasher in accordance withclaim 1, the controller comprising a processor and a memory, said memory including a plurality of heater element dry cycle operation values for a plurality of thermistor readings.

3. A dishwasher in accordance withclaim 1 further comprising a rinse aid product dispenser and a transducer operatively coupled to said rinse aid product dispenser.

4. A dishwasher in accordance withclaim 3, said controller further configured to operate the heater element for a selected dry cycle time period based upon the transducer reading.

5. A dishwasher comprising:

a wash chamber;

a thermistor for determining a temperature of said wash chamber;

a heater element located within said wash chamber;

a fan unit; and

a controller operatively coupled to said heater element, to said thermistor, and to said fan unit, said controller configured to execute a variable dry cycle wherein the heater element is energized for a selected time period determined by a thermistor reading of a final rinse water temperature and the fan is energized for a selected time period determined by the thermistor reading.

6. A dishwasher comprising:

a wash chamber

a thermistor configured to determine a final rinse water temperature;

a heater element located within said wash chamber;

a fan unit;

a rinse aid product dispenser;

a transducer operatively coupled to said rinse aid product for determining an amount of a rinse aid product in the dispenser; and

a controller operatively coupled to said heater element, to said thermistor, to said fan unit, and to said transducer, said controller configured to execute an energy efficient dry cycle wherein said fan unit and said heater element are energized for a time determined in response to the final rinse water temperature and signals from said transducer.

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